Section 3 Hydraulic Modelling Fundamentals

This chapter of the Manual discusses key considerations that should be addressed during the design phase of a hydraulic modelling study, prior to the commencement of the model build. Consideration of how the model is to be schematised and selection of key model parameters may have a significant influence on the accuracy, stability and simulation time of the model, and may avoid redundant work later in the study.

3 Hydraulic Modelling Fundamentals

  3.1 Schematisation

    3.1.1 General Guidance

    3.1.2 Model Dimensions: 1D, 2D or 3D?

      3.1.2.1 One Dimensional (1D)

      3.1.2.2 Two Dimensional (2D)

      3.1.2.3 Three Dimensional (3D)

    3.1.3 Coupled 1D-2D

    3.1.4 Quadtree Grid

  3.2 Model Resolution (Discretisation)

    3.2.1 1D Networks

    3.2.2 2D Cell Sizes

    3.2.3 Sub-Grid Sampling (SGS)

      3.2.3.1 Benefits of SGS

    3.2.4 Cell Size Results Convergence

  3.3 Solution Accuracy

    3.3.1 Fluid Flow Physical Terms

      3.3.1.1 1D Continuity Equation

      3.3.1.2 1D Momentum Equation

      3.3.1.3 2D Continuity Equation

      3.3.1.4 2D Momentum Equation

    3.3.2 Forms of the Equations

      3.3.2.1 Diffusive Wave Equation

      3.3.2.2 Kinematic Wave Equation

    3.3.3 Numerical Accuracy

  3.4 Timestep

    3.4.1 Fixed versus Adaptive Timestepping

    3.4.2 TUFLOW 1D (ESTRY) and EPA SWMM

    3.4.3 TUFLOW Classic 2D

    3.4.4 TUFLOW HPC 2D

      3.4.4.1 Timestep Efficiency Output

  3.5 Simulation Times